The grandstand, stadium and arena seating industry has traditionally relied on two main types of construction to provide adequate walking surfaces, or treads, and associated riser surfaces therebetween. The first of these is a reinforced concrete system utilizing concrete for both the horizontal tread and vertical riser portions. Concrete provides excellent performance in relation to vibration, noise transfer, and deflection. However, concrete also has its drawbacks. For example, in a typical concrete system, two or three row precast pieces spanning twenty to fifty feet are poured at the factory and shipped to the jobsite for installation. The pieces include very thick reinforced concrete treads and risers. Caulk must then be used to seal the horizontal joints where the precast pieces meet and prevent water seepage. The forms needed to pour these pieces are fairly expensive and typically cannot be reused from one project to the next due to custom configurations in the seating bowl. Some systems utilize concrete treads which are poured on site, which causes other concerns regarding the unpredictability of jobsite temperature and humidity conditions in addition to the added cost of on-site concrete pouring equipment.
In addition, an all-concrete system requires that epoxy or expansion anchors be used to attach the seats or benches to the concrete treads and risers, a process that typically requires expensive field drilling and time for the epoxy to cure. The concrete system is also extremely heavy and difficult to install and requires a stronger steel or concrete understructure for support.
The other type of construction commonly used involves metallic treads and risers, often aluminum, supported by a steel understructure. The aluminum treads typically span only about six feet, and are typically supported by steel stringers positioned on six foot centers. The aluminum system provides more cost effective options for installation, final adjustment, and seat mounting, although typically cannot match the performance characteristics of the concrete system. Aluminum systems also offer more options in terms of vertical surface coloring and may be more easily modified on a project to project basis.